Film and film/nonwoven laminates are used in a wide variety of applications, not the least of which is as outercovers/backsheets for limited use or disposable products including personal care absorbent articles such as diapers, training pants, swimwear, incontinence garments, feminine hygiene products, wound dressings, bandages and the like. Film/nonwoven laminates also have applications in the protective cover area, such as car, boat or other object cover components, tents (outdoor recreational covers), and in the health care area in conjunction with such products as surgical drapes, hospital gowns and fenestration reinforcements. Additionally, such materials have applications in other apparel for clean room, health care and other uses such as agricultural fabrics (row covers).
In the personal care area in particular, there has been an emphasis on the development of film laminates which have good barrier properties, especially with respect to liquids, as well as good aesthetic and tactile properties such as hand and feel. There has been a further emphasis on the “stretch” comfort of such laminates, that is, the ability of the laminates to “give” as a result of the product utilizing such laminates being elongated in use, but also to provide a necessary level of vapor permeability to maintain skin health of a product user.
It is known that breathable polymeric films may be made by utilizing a variety of thermoplastic polymers in combinations with filler particles. These and other desired components, such as additives can be mixed together, heated and then extruded into a monolayer or multilayer filled film. Examples are described in WO 96/19346 to McCormack et al., incorporated by reference herein in its entirety. The filled film may be made by any one of a variety of film forming processes known in the art such as, for example, by using either cast or blown film equipment. The thermoplastic film can then be stretched either alone or as part of a laminate to impart breathability or other desired properties. The films are often stretched in a machine direction orienter-type apparatus, or other stretching device, which stretches the film, thereby creating a pore-like matrix in the film body at the locations of the filler particles. While such breathable films and film/laminates are known to be used as personal care outercover materials, thereby allowing the personal care products to “breathe” and making such products more comfortable to wear, there has been difficulty producing such materials from “elastic” -type materials. Often, such breathable films are produced from polyolefin materials that can be extended without the ability to retract. While such film materials offer the comfort of air/gas circulation, and may offer the ability to extend only, they may limit or restrict movement of a user wearing articles made from such materials. If they are extended to a great extent, they may sag within the product, since they lack the ability to retract, and may in some circumstances, contribute to leakage. Such sagging sacrifices both the aesthetic appearance and the comfort level of the product.
It is has been found that if filler is placed in elastic polymer film formulations, the pores that are formed around the filler particles during a film formation stretch operation (such as in a machine direction orienter) are temporary, and close after stretching, as a result of the elastic attributes of the polymer component in the film. Without the pore structures, the film becomes non-breathable. It therefore is widely recognized that properties relating to elasticity and breathability are often conflicting. As a result of these attributes of highly elastic polymers, when breathable and elastic film materials have been sought for personal care product applications, manufacturers have often turned to inherently breathable elastic materials, that allow gasses to pass or diffuse through their structures, without the necessity for pores (which risk collapse). Such inherently breathable films may be more costly than other material films, often do not provide the level of breathability desired for consumer product applications, and often have to be fairly thin in order to achieve an acceptable level of breathability. Such thin films often lack the requisite strength/tear strength characteristics desired in personal care products.
It would therefore be desirable to produce filled breathable elastic films of varying basis weights, without the risk of pore collapse. It would further be desirable to produce breathable elastic films that may be efficiently laminated to nonwoven sheet structures without sacrificing elastic functionality. It is to such needs that the present invention is directed.